linux/fs/notify/group.c
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   1/*
   2 *  Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
   3 *
   4 *  This program is free software; you can redistribute it and/or modify
   5 *  it under the terms of the GNU General Public License as published by
   6 *  the Free Software Foundation; either version 2, or (at your option)
   7 *  any later version.
   8 *
   9 *  This program is distributed in the hope that it will be useful,
  10 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 *  GNU General Public License for more details.
  13 *
  14 *  You should have received a copy of the GNU General Public License
  15 *  along with this program; see the file COPYING.  If not, write to
  16 *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
  17 */
  18
  19#include <linux/list.h>
  20#include <linux/mutex.h>
  21#include <linux/slab.h>
  22#include <linux/srcu.h>
  23#include <linux/rculist.h>
  24#include <linux/wait.h>
  25
  26#include <linux/fsnotify_backend.h>
  27#include "fsnotify.h"
  28
  29#include <linux/atomic.h>
  30
  31/*
  32 * Final freeing of a group
  33 */
  34void fsnotify_final_destroy_group(struct fsnotify_group *group)
  35{
  36        /* clear the notification queue of all events */
  37        fsnotify_flush_notify(group);
  38
  39        if (group->ops->free_group_priv)
  40                group->ops->free_group_priv(group);
  41
  42        kfree(group);
  43}
  44
  45/*
  46 * Trying to get rid of a group.  We need to first get rid of any outstanding
  47 * allocations and then free the group.  Remember that fsnotify_clear_marks_by_group
  48 * could miss marks that are being freed by inode and those marks could still
  49 * hold a reference to this group (via group->num_marks)  If we get into that
  50 * situtation, the fsnotify_final_destroy_group will get called when that final
  51 * mark is freed.
  52 */
  53static void fsnotify_destroy_group(struct fsnotify_group *group)
  54{
  55        /* clear all inode marks for this group */
  56        fsnotify_clear_marks_by_group(group);
  57
  58        synchronize_srcu(&fsnotify_mark_srcu);
  59
  60        /* past the point of no return, matches the initial value of 1 */
  61        if (atomic_dec_and_test(&group->num_marks))
  62                fsnotify_final_destroy_group(group);
  63}
  64
  65/*
  66 * Drop a reference to a group.  Free it if it's through.
  67 */
  68void fsnotify_put_group(struct fsnotify_group *group)
  69{
  70        if (atomic_dec_and_test(&group->refcnt))
  71                fsnotify_destroy_group(group);
  72}
  73
  74/*
  75 * Create a new fsnotify_group and hold a reference for the group returned.
  76 */
  77struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops)
  78{
  79        struct fsnotify_group *group;
  80
  81        group = kzalloc(sizeof(struct fsnotify_group), GFP_KERNEL);
  82        if (!group)
  83                return ERR_PTR(-ENOMEM);
  84
  85        /* set to 0 when there a no external references to this group */
  86        atomic_set(&group->refcnt, 1);
  87        /*
  88         * hits 0 when there are no external references AND no marks for
  89         * this group
  90         */
  91        atomic_set(&group->num_marks, 1);
  92
  93        mutex_init(&group->notification_mutex);
  94        INIT_LIST_HEAD(&group->notification_list);
  95        init_waitqueue_head(&group->notification_waitq);
  96        group->max_events = UINT_MAX;
  97
  98        spin_lock_init(&group->mark_lock);
  99        INIT_LIST_HEAD(&group->marks_list);
 100
 101        group->ops = ops;
 102
 103        return group;
 104}
 105
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